


binary star

by bylaude



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Developing Friendships, F/M, Female My Unit | Byleth, Fire Emblem: Three Houses Golden Deer Route, Friends to Lovers, Male-Female Friendship, POV Claude von Riegan, Post-Timeskip | War Phase (Fire Emblem: Three Houses), Pre-Timeskip | Academy Phase (Fire Emblem: Three Houses), Slow Burn, byleth in the Fuck Crests Club, claude wants to play speed social chess but byleth is too far removed from emotions to participate, no beta we die like Glenn
Language: English
Status: In-Progress
Published: 2020-03-06
Updated: 2020-03-20
Packaged: 2021-02-28 21:48:06
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 3,784
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23044267
Author URL: https://archiveofourown.org/users/bylaude/pseuds/bylaude
Summary: [binary star|noun: a system of two stars in which one star revolves round the other or both revolve round a common centre]Claude, Byleth — and the stages of falling in love.Told in Claude's POV. May not be in chronological order (?).
Relationships: My Unit | Byleth & Claude von Riegan, My Unit | Byleth/Claude von Riegan
Comments: 20
Kudos: 105





	1. notice

**Author's Note:**

> figured that I should finally (digitally) pen down my Bylass x Claude ideas because uhhhhh kinda sad if I don't live up to my username lol ~~if you came from my fe3h tumblr i'm so sorry it took me this freaking long lmao~~
> 
> Title is a reference to Byleth being called the "Fell Star" and Claude's Failnaught combat art "Fallen Star." (GD have a LOT of star references in general, actually. God-Shattering Star, anyone?)
> 
> A binary star is also called "double star" and because they revolve around one another, they can be perceived as a single light source depending how far away you are viewing them from - hence, why it is referred in singular terms "binary star / double star" because it can be seen as a star made up of...two stars lol (referring to how I want to write them here, I guess, they become a packaged deal duo).

**—X—**

_prologue  
_ _**notice** _

When they first meet, Claude doesn't think too hard about her except as another person he must charm and fool with his smiles.

Having walked a complicated path of life, Byleth is far from the first mercenary Claude has had the (sometimes dubious) opportunity to acquaint himself with. They come in all shapes and sizes — loud laughs and sharp grins, cruel words and unfounded confidence, inhumane apathy and cutthroat pragmatism.

Dimitri assumes her intimidating and perhaps unfeeling, while Edelgard scrutinises her with a face that says, _now how can I make use of you?_

Claude likes to think he has the best perception of them all, having stayed well in the shadows during the fight against the bandits, following at her heel as she fearlessly dived headfirst into the center of the battlefield.

Byleth is _militant_. She fights a lot like a knight for a sellsword who's presumably been put to more uncouth work — courtesy of her father's training, maybe, whom he finds out was a Knight of Seiros himself. Not once does she express a flicker of interest or emotion, nodding simply as she carries out Jeralt's careful instructions on the field. Her voice is just as quiet and flat as he imagines when she finally does speak, looking straight at them as she tells them what to do with the air of someone expecting to be obeyed as well as she obeys her father. It is not quite trust that leads her to entrust Claude with the task of covering her back, but an oddly noble absolution in the idea of _you will do what you must as I will do what I must_.

He stares into her eyes and sees a well-trained warrior — a soldier, passive and without a cause to fight for but gold and survival. She's aloof, locked into an intangible bubble where the world's troubles are not her own.

She's not a threat, Claude decides, not unless she is hired by another — which is a prospect that grows increasingly likely when Dimitri becomes utterly besotted with her combat ability and Edelgard regards her with a newfound respect and interest.

(In the future, he would look back upon this moment with irony. To think he had only been concerned of His Royal Highness and Her Imperial Majesty, whom he had not yet been able to place as friend or foe, when in truth, Byleth herself had been the biggest player on the chessboard.)

He's disconcerted when she gazes back at him, her stare strangely honest and straightforward despite her inexpressive face and palpable distance. There's a discomforting feeling in his gut that she's peering right through him, which doesn't often happen unless he means it to. Her eyes are not powerful like Edelgard's or forcibly bright like Dimitri's, but invasive in a way he finds deeply unsettling and unfamiliar.

_I see you,_ she seems to say with her eyes, and it does not at all gladden him to know that she's baring her own soul for his perusal in return, when he finds it too empty and lacking to even be human.

Unusually for him, Claude is the first to break gaze.

She's dangerous, he thinks, though not in a way he expects.

**—X—**

(" _So, capable stranger," he starts in a nearly jocular manner, with an easy smile that hides his disquiet, "Let’s get right to it. Where does your allegiance lie?"_

_Unfooled, the young woman observes at him, her expression unchanging, and replies blandly, "Do I need one?"_ )

**—X—**


	2. curious

**—X—**

_01:  
_ _**curious**_

He's startled to find her seated at the teacher's table on the first day of class. He's startled to find that anyone had arrived before _him_.

"I am not a student," Byleth tells him, unprompted, and this surprises a laugh out of him.

"No, I figured not!" Claude grins, hopping onto the nearest desk to her and propping his chin upon a fist.

It makes him contemplate the week during which he had spotted her wandering about, speaking to (and sometimes unnerving) the students who had repeatedly asked if she were to join as a latecomer student. He had once overheard Hilda question if she were to be a knight and had to stifle a knowing smile. Being a house leader has its perks and Claude had been amongst the few who had been told of her true appointed duty.

He sees her stare at him for a moment before blinking, as if in remembrance, and raises his brows, amused. "Did you forget?"

"Forget?" She parrots — and he almost thinks she's playing the ignorance game, except that despite her piercing gaze and odd mannerisms, Claude finds that she's a bit too, dare he say it, _spacey_ to attempt acting dumb. It probably would not even occur to her.

To be honest, she actually seems somewhat _simple-minded_. Maybe it comes with the territory of only ever needing to fight on the field. She may dance with her blades, deadlier than most warriors he's met, but Claude suspects she knows nothing of the noblemen's waltz of words.

After all, in spite of his wariness for her sharp, discerning eye, his initial impression of her — too straightforward and honest — have so far held steadfast.

"Did you forget that I've been informed, along with the other house leaders, that you are to be a professor?" He asks, putting it as plainly as he can. She does not take offence.

"Oh, that," Byleth nods and, offering no explanation or excuse, simply admits, "Yes."

Claude tilts his head, deliberating. He almost doesn't care to act around her. Though she seems simple, Byleth also gives off the air of someone _too_ simple to be fooled and he thinks it might be an effort in vain at this rate. She does not say more, leaving him with nothing to go on or latch onto — nothing to sink his proverbial teeth into.

Perhaps it is good that she is not with the other houses. Claude doesn't doubt that Edelgard and the spindly man who is always by her side would waste no time sinking _their_ claws in her, with barbed words and hidden agendas — and a combination of the virtuous Fearghan prince with his rosey-eyed gaze and this ruthless woman who is otherwise proving impotent outside of combat would either be very fearsome or _very ineffectual_.

Well, he can't say he's displeased with this turn of events. Claude is definitely more interested in the enigmatic daughter of the runaway captain of the Knights of Seiros, more so than he is of the perpetually spurned songstress-turn-physician or the crest scholar who was once an imperial noble or that strange masked swordsman who is somehow _more_ acerbic than her. Having Byleth near him means one less potential threat and having a capable fighter at hand.

And, besides, it'll be good to have someone with actual field experience to teach them. Claude is nothing if not pragmatic.

"Class has not started," she says, managing to be both blunt yet oblique, and Claude smiles, deciding to fool around a bit. Best that she learns to get used to the waltz with him than another. Perhaps she could learn a thing or two.

"No, I guess not," he chirps and, to his delight, spots the first sign of emotion on her inanimate, doll-like face. The skin between her brows crinkle in frustration.

"You do not have to be here this early," Byleth goes on and he's glad to know she's not _that_ dense as to immediately demand him to leave. Until she gains a bit of respect around here, it might be a better idea to tread a little carefully around the blueblood. Although he's told her to dispense with the formalities with him, not all of them would appreciate being told off, even by a professor.

"Oh?" Claude lilts, grinning with teeth, "Well, I already am here, so I may as well stay. Besides, I want to save my seat! First row, smack-dab in the center! Because I am an attentive and diligent student, obviously."

Byleth stares at him. "Diligent students do not usually sit on the table."

"Not usually, no," he agrees easily with a sagely nod — and make absolutely no move to get off.

Byleth falls silent and promptly begins to ignore him. It puts him off slightly, because while he anticipates an eventual cold shoulder, he doesn't expect her to drop the conversation with such certainty and suddenness and it feels a bit like having a door unceremoniously slammed into his face. He doesn't let this show, continuing to smile at her with an air of unflappability, and barrels onward without regard for her lack of response.

"That said," he starts — and considers it a minor victory when she visibly frowns. It's small and hardly there, but it's a reaction nonetheless. "I'm surprised you chose the Golden Deer. Don't tell me — you chose our house just to get to know me better, right?"

Byleth stops rifling through her papers, looking up to stare at him once more. Claude blinks, mouth falling open.

"No, _did you_?" He makes a show of gasping, then lets loose a delighted laugh. "I was only kidding, but I'm flattered!"

Her voice is flat as she deadpans. "How do you know?"

"Hm?" He prompts, though he feels his smile begin to waver under her astute gaze.

"How do you know I was given a choice?" She asks, and although her voice is soft and nothing about her stance is threatening, he abruptly feels like he's being interrogated.

Thinking quick, he replies cheekily, "You just confirmed that for me."

She does not believe him; that much is obvious. Still, there is no proof that he is lying through his teeth, and he's not _quite_ ready to admit he might've loitered about Professor Manuela and Hanneman for a while and eavesdropped on a conversation or two to gain some insight on the new mystery teacher's appointment.

To his surprise, she does not push. Byleth lowers her eyelids in consideration — and sighs.

"A liar," she murmurs aloud, seemingly to no one. "Of course."

"Aw, Teach," Claude protests, thinking her strange but not saying it to her face. "That stings. Let a man keep some secrets."

"You'd make a good spy," she comments, a complete non-sequitur, and he has a sneaking suspicion that she's not joking.

He doubts if she _knows_ how to make a joke.

Claude pretends it is one and goes along with it anyway. "Why, thank you! I'll take that as a compliment. I thought I might be a bit too high profile for that — heir to the Alliance and all — but it means a lot that you think I have the stealth for it. By the way, do you know what you're doing? You've been aimlessly going through your papers for a while now."

Byleth stops. He expects her to shoot a quip about how he's distracting her or finally order him to make himself scarce, but instead she stares down at her hands. It makes her look a bit helpless, like an unwitting sheep thrown to the wolves, which is an odd thing to think because her expression is like stone and so is her spine.

"I was given the syllabus," she says, matter-of-factly. "And I went through the topics over the past week."

"All of it?" Claude asks, incredulous. She nods, her face almost laughably serious, as he whistles. "I'm not saying that's not impressive, because it _is_ , but that's not the same as teaching or giving lectures, is it. Did anyone coach you on that? No? Not even the basics?"

He's dismayed to see her shake her head a third time. She really _has_ been thrown to the wolves. He thinks back to watching her run about during the last few days, gathering things and perusing through the training inventory. Byleth had always seemed busy, giving him little opportunity to try and insert himself in any conversation with her, and he remembers one instance where he had caught sight of her looking through notes in the mess hall, her food laying untouched before her.

Claude sighs, running a hand through his hair. "Ah, what are they thinking... Guess I have to do everything by myself. Here, let me see."

She hesitates, turning in a different direction as he approaches. "I... Should I?"

If he had looked up, he would've thought it peculiar to see her staring at the blackboard as though it is a live person and capable of answering her question. Instead, he's too preoccupied with tugging her papers out of her hands to notice. "It's fine, it's _fiiine_. You've met my housemates, haven't you? They're a rowdy bunch. You have to make the lesson interesting to keep their attention and there's no harm in accepting a little help, is there?"

Byleth doesn't answer for a while and he thinks that the end of it.

Then, she speaks.

"I suppose not," she says, and the sudden sensation that she's addressing someone else _not him_ is so strong that he turns, whipping his head about and expecting to see a newcomer.

But it is still over half an hour too soon for class and there is only him and her in the room. Flummoxed, Claude blinks, staring into her unreadable face, before forcing himself to shake it off.

A chill crawls down his back. Although he already knows this, Claude finds himself thinking yet again that there's something not quite right about Byleth.

**—X—**

( _"Say," he mentions at one point, shortly before Lysithea walks into the classroom, ever the early bird. "Why were you here so early in the morning? Were you nervous?"_

_Even though he knows he must be right by the way she shifts minutely but tellingly on her feet, Byleth stares back at him, almost defiantly, as she asks, "Why were you?"_

_"Fair point," he relents with a chuckle, deciding to pity her and spare her pride. "But if you must know, I guess you can say I was...scouting the area."_

_"You'd make a good spy," she repeats and he wonders if he's made a mistake getting that idea into her head._

_Hopefully not._ )

**—X—**

**Notes for the Chapter:**

> Byleth is absolutely talking to Sothis in front of Claude lol.
> 
> Title uses both definitions of the word. She's curious, as in strange, while he's curious _of_ her.
> 
> My memory is dusty but iirc Claude seems to be the only lord who knew Byleth was given a choice as to which house to teach. Edelgard mentions that maybe Byleth would be "assigned" to her house, so she appeared to be under the impression that it would be decided by other faculty/Rhea. Somehow, I don't doubt that Claude regularly goes about, gathering information for himself lmao. He had a whole-ass week to do that, after all.


	3. intrigue

**—X—**

_02:  
_ **_intrigue_ **

Claude keeps a keen eye for possible sources of information.

There's too much unexplained about Byleth for him to possibly turn a blind eye to the mystery dangling before his face. A strange young woman of dubious origin and background, virtually unknown until she is abruptly thrust into the role of an educator of Fódlan's future leaders? And at the behest of the Archbishop herself, no less, if the rumours are to be trusted. It's fishy — even Lorenz can admit to that and he's notoriously difficult to converse with, with the way he stares at Claude like he'd drive a knife into his back the moment he exposes it to the Riegan heir.

Which, well, _fair_ , because Claude looks at everyone like that, too — it doesn't help that he's admittedly not too different from Byleth in the "dubious origin" aspect — and one unfriendly classmate, however irksome, is hardly the worst that he's ever had to deal with.

He's mostly annoyed that Lorenz doesn't have the _grace_ to hide it.

Claude doesn't question his classmates so much as carefully keep an ear out for their collective opinion on their unexpectedly youthful professor. Any information is valuable information, in his book, and it helps that the Golden Deer are still abuzz over Byleth's appointment; he hardly needs to prod conversation into the right direction at all before they're speaking of her, whispering and gossiping alike — for, despite the undertone of hesitation on her first day when he had to briefly coach her on how to conduct a lesson, the general consensus is that Byleth has so far proven to be quite decent at teaching.

She's clear and concise, leaving no room for any doubts when asked a question, and tolerates even Lysithea's rapidfire inquiries with unflappability. Perhaps her only shortcoming is her lack of time management, because she becomes surprisingly talkative when asked the right things, going off on tangents on geography and botany.

Claude has made it a game to see how long he could make her go overtime — and on her fourth day, she winds up speaking for over half an hour after class was supposed to end, after he'd posited an innocent query on the medicinal benefits of the poisonous Morfis bindweed. Byleth's intensity was such that every soul in the room either did not keep time or dared not speak up for fear of interrupting her.

And Claude — well, he knows a lot about the bindweed, now, so no complaints there.

"If you _must_ do that," Hilda confronts him after class, exasperated but not terribly so that she would stop speaking with him. "Can't you do it before combat training? I'd rather the Professor cut time from _that_ than our breaks."

Claude laughs. "For shame, Hilda! And have the Golden Deer be unprepared for the mock battle? You must be joking."

She snorts, or as much as a lady could without seeming inelegant. "Is there a prize to be had? You've gotta admit there's little point in putting in so much effort when all we'd get is _bragging rights_."

He grins back. "Ah, but imagine if those rights were to be won by the other houses. Do you see, Hilda? How _insufferable_ they would be! Best we win them instead, when we would be responsible and humble with our hard-earned glory."

Someone scoffs. "Do you two have _anything_ better to do?"

Barreling out of the class doors, Lysithea sweeps past them without waiting for an answer, apparently having finally milked every ounce of knowledge she could from their professor. Hilda huffs at this, though Claude doesn't take it personally. He may not have known her for long, but Lysithea always moves like a girl on a mission — tenacious and purposeful with every action. In a way, he and her are not so unlike each other.

Claude simply hides it better—

"Don't you have anything better to do?"

...Claude does not hide it as well as he'd hoped.

Jeralt the Blade Breaker stares down at him dryly, unamused to find one of his daughter's students lurking in the corner of a tavern at some ungodly hour of the night (or early morning?), blatantly spying on his mercenary company which now find themselves under the Church's employment. Claude had figured that the liquor would loosen their tongues and he was right, managing to overhear scattered tales of the "Ashen Demon" and their disbelief that Byleth had landed a cushy job at the Officers Academy, along with other more _intriguing_ details.

What Claude had _not_ accounted for was Jeralt's surprisingly high tolerance. He had been banking on the hope that they would be too drunk to notice his presence even if he were to linger too long, but despite the several pints he had witnessed Jeralt down like it was _water_ , the knight's gaze is as clear and sharp as glass.

Most of the other mercenaries at the other tables, still howling with laughter and sloshing mead in their mugs, remain blissfully unaware of their leader's confrontation. Claude distantly hears them make bets about how long it'd take for Byleth to "make one of the noble brats shit their pants."

Claude finds himself thinking he's only one good scare away from doing just that.

 _Ah, so this is where she got those eyes from,_ he notes, pasting a smile on his face even as he feels Jeralt's stare on him like a dagger to his throat. He had thought Byleth merely disconcerting — in comparison, her father is downright _terrifying_.

Claude decides then that it would be best to keep on his professor's good side, if she's anything like Jeralt when provoked.

"Whatever could you mean?" He lilts, refusing to again break eye contact like he had with Byleth long before. "I'm just enjoying the weekend on a nice night out. Say, care to share a drink with me—?"

Jeralt ignores the invitation. He expects that. What makes Claude jump is the way Jeralt unflinchingly slaps a palm over his mug as Claude raises it, slamming it back down on the table. He gulps. "Look, kid. Are you even old enough to drink?"

Claude lets his smile fall. "It's the baby face, isn't it?" He bemoans. "Sir, I solemnly swear that I am _absolutely_ old enough. I have been for quite a while, in fact!"

That is not a lie. By the customs of his homeland, Claude had already became a man at the age of fifteen — so no, it is not a lie, only an untruth.

After all, Fódlan's own customs dictate he won't quite be considered an adult until he reaches his eighteenth birthday, which isn't for a few months more.

But, well, what would a runaway mercenary know about one outsider's date of birth?

"Hm," Jeralt stares at him, scratching his beard with his free hand. For a wild moment, Claude envisions the man picking him up like a sack of potatoes and unceremoniously dumping him at Byleth's doorstep, perhaps with an order to take her students in hand. But, in the end, he only rolls his eyes and sighs heavily. "You're one of Byleth's, aren't you? I heard you would be practicing with the knights tomorrow. Don't stay too late. Or do, but don't cry if you perform poorly and she decides you require _extensive training_."

He's almost scared to know what that entails. Claude resolves to never find out.

Recognising that he's being let off with a slap on the wrist, Claude flashes his best smile and watches as Jeralt returns to his table.

The man's eyes stay on him until he leaves with haste.

No need to push his luck. He's learnt enough — for now.

**—X—**

( _"Our Byleth, can you imagine? How long would those kids last under her, you reckon?"_

_"It's different here, so who can say? She never held back against the whelps in our ranks, but it won't look good if she makes things too tough for the students here."_

_"What a time to be alive. The fearsome Ashen Demon turned a mother duck for the little hatchlings."_

_"If not her lack of expression, then surely her presence in a battle would terrify them. And if not_ that _, then that horrible Crest of hers—"_

_Jeralt rises from his seat from another table, his hulking figure nearly menacing._

_"Enough," he hisses and the mercenaries fall silent._

_Then Jeralt turns his eyes upon him._

_Claude has never felt more like a deer in the face of a bear._ )

**—X—**

**Notes for the Chapter:**

> ~~claude: mum come pick me up im scared~~
> 
> So I lied. I might try to go on in a chronological order, just to build up Claude's change of opinion of Byleth over time, as well as her growth from his POV.
> 
> Cameo/mentions of other Golden Deer! They're my first house and I will always love them. (Marianne is my baby, though she's not here yet.) Might consider side pairings, but I'm not thinking that deeply on it since this is very Claude-centric. I tried to execute a Gilligan cut from the classroom scene to the tavern scene, but let me know if that was too confusing? Not sure if it translated well with my writing style lol.
> 
> Maybe I'm not looking in the right places, but I never see fanmade Claude-Jeralt content. I see fanfics or art of Edelgard feeling remorseful or Dimitri in that classic father-in-law scenario, but Claude... Hmmmm. I can't picture them getting along lmao. Especially with all of Jeralt's secrecy. Claude would poke his nose where it doesn't belong.


End file.
